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Enigma said:
Sorry, this question might have been asked before.
How do people measure flashlight brightness? Is there an inexpensive machine for it?
--- Enigma
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Complicating your quest for understanding is the problem that folks here don't agree on what "brightness" means. It is not a scientifically defined term like total luminious flux" or "intensity". See link below for some discussion of the interpretation of the word "brightness"
Brightness?